Editing Hydride (section)

=== Ionic hydrides ===
These are stoichiometric compounds of hydrogen. Ionic or '''saline hydrides'''<ref name="UllmannH2">{{cite book |doi=10.1002/14356007.a13_297.pub3 |chapter=Hydrogen, 1. Properties and Occurrence |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2013 |last1=Lauermann |first1=Gerhard |last2=Häussinger |first2=Peter |last3=Lohmüller |first3=Reiner |last4=Watson |first4=Allan M. |pages=1–15 |isbn=978-3-527-30673-2 }}</ref> are composed of hydride bound to an electropositive metal, generally an [[alkali metal]] or [[alkaline earth metal]]. The divalent [[lanthanide]]s such as [[europium]] and [[ytterbium]] form compounds similar to those of heavier alkaline earth metals. In these materials the hydride is viewed as a [[pseudohalide]]. Saline hydrides are insoluble in conventional solvents, reflecting their non-molecular structures. Ionic hydrides are used as bases and, occasionally, as reducing [[reagent]]s in [[organic synthesis]].<ref>{{cite book|last=Brown|first=H. C.|title=Organic Syntheses via Boranes|url=https://archive.org/details/organicsyntheses0000brow|url-access=registration|publisher=John Wiley & Sons|location=New York|date=1975|isbn=0-471-11280-1}}</ref>

{{block indent|[[Acetophenone|C<sub>6</sub>H<sub>5</sub>C(O)CH<sub>3</sub>]] + [[Potassium hydride|KH]] → C<sub>6</sub>H<sub>5</sub>C(O)CH<sub>2</sub>K + H<sub>2</sub>}}

Typical solvents for such reactions are [[ethers]]. [[Water]] and other [[protic solvent]]s cannot serve as a medium for ionic hydrides because the hydride ion is a stronger [[Base (chemistry)|base]] than [[hydroxide]] and most [[hydroxyl]] anions. Hydrogen gas is liberated in a typical acid-base reaction.

{{block indent|<chem>NaH + H2O -> H2_{(g)}{} + NaOH</chem>}}
{{block indent|1=Δ''H'' = −83.6&nbsp;kJ/mol, [[Gibbs free energy|Δ''G'']] = −109.0&nbsp;kJ/mol}}

Often alkali metal hydrides react with metal halides. [[Lithium aluminium hydride]] (often abbreviated as LAH) arises from reactions of [[lithium hydride]] with [[aluminium chloride]].

{{block indent|4 [[Lithium hydride|LiH]] + AlCl<sub>3</sub> → LiAlH<sub>4</sub> + 3 LiCl}}